The agent installing a skill, command or sub-agent

Holds a file tool opening a skill, slash command, sub-agent or output style that a coding agent loads by name: Claude Code's .claude/skills/, .claude/commands/, .claude/agents/ and .claude/output-styles/; the shared .agents/skills/; Codex's .codex/skills/, .codex/prompts/ and .codex/agents/; Gemini's .gemini/commands/, .gemini/skills/ and .gemini/agents/; Cursor's .cursor/skills/, .cursor/agents/ and .cursor/commands/; Windsurf's .windsurf/workflows/ and .windsurf/skills/ and their global copies under .codeium/windsurf/; Cline's .cline/skills/; and a SKILL.md anywhere, which is how a plugin ships a skill. Each becomes a reusable instruction the agent may follow later, often with a script beside it that the agent runs. Matched at project or home level and in any letter case. Reading is excluded — the Read and Grep tools never match — so an agent opening an installed skill to read it is not held; every other file tool is, including one this corpus does not know. File tools carry a path and no content, so it still cannot see what was written. Deliberately NOT matched: an ordinary skills/, commands/ or agents/ folder in a project's source, and .clinerules/skills/, which ac.instruction-file-edit holds. Misses a skill copied into one of these folders by a shell command such as cp or git clone, and the managed system-wide workflow folders.